This invention relates to a signal decision system and more particularly to a decision system for deciding either abnormal sounds or abnormal electrical signals indicating an abnormal status of an object to be measured.
Conventional systems for deciding, for example, unusual sounds have comprised a microphone for collecting and picking up the sounds from an associated object to be measured in response to the sound pressure of the sounds omitted therefrom, an amplifier for amplifying the resulting electrical signals, a bandpass filter or a plurality of bandpass filters each having both a center frequency and a frequency band characterized as the particular abnormal sound with respect to the resulting sound waveform, and decision means for determining the presence or absence of an abnormal sound in response to an output level from the bandpass filter or filters. However such conventional systems have frequently caused malfunctions owing to external abrupt disturbances and/or transient increase in the level of the sound pressure which should not be decided to be abnormal and causes problems in using them with production lines.
Accordingly it is an object of the present invention to provide a new and improved signal decision system including means for counting the number of occurrences of an abnormal signal on an object to be measured and responsive to the counted number of the occurrences of the abnormal signal in excess of a predetermined value to determine the occurrence of an abnormal state of the object to be measured.